In an increasing number of countries, ground transportation moves at speeds over than 300 km/h, e.g., Japan Tohoku Shinkansen (320 km/h), German Intercity-Express (ICE) (330 km/h), Automotrice Grande Vitesse (AGV) Italo (400 km/h), and Shanghai Maglev (430 km/h). Accordingly, an increasing number of mobile terminals are used in such high speed environments. However, in the 3rd Generation Partnership Project (3GPP) specifications, e.g., Evolved Universal Terrestrial Radio Access (E-UTRA), performance of communication is only guaranteed up to a maximum speed of 350 km/h. Because of this, 3GPP initiated a new study item concerning performance enhancement in high speed scenarios. See RP-142307, 3GPP TSG RAN Meeting #66, Maui, Hi., Dec. 8-12, 2014, the contents of which are incorporated herein by reference.
In this effort, various channel models have been proposed and tested/simulated. See, e.g., R4-150122, “New channel mode for SFN deployment”, Huawei; R4-150540, “Channel model for high speed train”, Mediatek; and R4-150554, “High speed train scenarios”, CMCC, each of which was presented at TSG RAN WG4 Meeting #74 in Athens, Greece, Feb. 9-13, 2015, and each of which is incorporated herein in its entirety. FIG. 1 illustrates a diagram of a high speed (HS) single frequency network (SFN), according to one embodiment of the present disclosure. FIG. 1 is based on FIG. 1 of R4-150122.
In FIG. 1, a high speed train 101 travels on tracks 110 where a series of remote radio heads (RRHs, labelled RRUs in drawing) run parallel with the tracks 110. In the system, a plurality of NRRHs are connected by fiber optics to form a single cell: RRU 121 to RRU (N) for cell 120 and RRU 131 to RRU (N) for cell 130. As can be seen in FIG. 1, a user equipment (UE) on train 101 passing by several RRHs is affected by the rapid changes of frequency due to Doppler shift as well as experiencing a time-varying multipath channel. In other words, the UE will experience a superposition of signals coming from the multiple RRHs, and, since the UE is rapidly moving along the railway, signal properties such as Doppler shift, time delay, and tap power will be dynamically changing. In such a HS-SFN scenario, traditional time domain channel interpolation schemes, such as linear interpolation and minimum mean-square error (MMSE) estimation based on Jake's model perform badly.